Question

question 25 of 30. you want to test how the mass of a reactant affects the speed of a reaction. which of the following is an example of a controlled experiment to test this? a. the mass of one reactant and the temperature of the reaction mixture are increased until the reaction is finished. b. the mass of one reactant at a time is varied, and the time it takes the reaction to finish is measured. c. the mass of all of the reactants is kept the same, and the mixtures are allowed to react for different lengths of time. d. the mass of all the reactants is varied, and the time it takes the reaction to finish is measured.

Explanation:

A controlled experiment tests how one variable affects another by varying only the independent variable (mass of reactant here) and measuring the dependent variable (reaction time), keeping others constant. Option B varies the mass of one reactant at a time and measures reaction time,符合 controlled experiment requirements.

Answer:

B. The mass of one reactant at a time is varied, and the time it takes the reaction to finish is measured.